[RE-wrenches] Cummins DC generator

Mon Oct 24 19:55:13 PDT 2011

They show them as being used specifically for off grid solar applications including remote homes, but I'm with you, I don't understand the voltage limitation.
They seem to think they are just replacing the battery while running, not actually charging it. Very weird. I even went through their case studies, and I'm wondering if they might end up with some long term sulfation problems. It seems they're only interested in reducing the battery size, not augmenting the PV charging; seems a waste of fuel.

I linked to these for Allan earlier just as "food for thought" I wasn't actually advocating their use. It does look like a decent generator, so possibly the voltage limitation could be overcome?
I remember another DC gen set, that ran a Honda motor to belt belt drive a truck alternator (late 90s). I recall them being something of a pain.

Here's another that looks interesting, and actually can be adjusted up to 64 vdc: http://polarpowerinc.com/products/generators/index.htm
Once again, I'm just sharing the info, not advocating these.

R. Walters
ray at solarray.com
Solar Engineer

On Oct 24, 2011, at 6:30 PM, bob ellison wrote:

> I downloaded the spec sheets on the DC generator, it’s either LP or natural gas. Also it’s regulated to 26 volts or 52 volts, so it’s about useless to charge batteries in an off grid system, unless you just need to feed power to the battery bank.
> 
> Bob Ellison
> 
> From: re-wrenches-bounces at lists.re-wrenches.org [mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Ray Walters
> Sent: Friday, October 21, 2011 7:41 PM
> To: RE-wrenches
> Subject: Re: [RE-wrenches] Three-phase off-grid
>  
> 
> HI Allan;
> 
> I haven't tried the large Exeltech inverters, but I could see some advantages to having a separate charging system, and keeping the inverters supplying stable power. Everytime a generator coughs or switches from one source to another, it seems to cause trouble. The generator could be sized smaller, since it wouldn't need any surge capability. It would always run the same charger, and the inverters would always run the same loads. I'd at least take another look at it for my next large project, but cost might be a limiting factor.
> Here's a Cummins diesel DC generator, just to think about: http://www.cumminspowerproducts.com/DCgensets/Other/10000500.pdf
> 
> Ray
> 
> On 10/21/2011 4:56 PM, Gary Willett wrote:
> 
> Alan: Thanks for setting me straight about 3-phasing the Outback Radian - I was not aware they are limited to parallel single phase applications.
> 
> Regards,
> 
> Gary Willett
> 
> On 10/21/2011 15:29, Allan Sindelar wrote:
> Gary,
> I was surprised by this information, as I had presumed that both units were for single-phase only. So I checked.
> 
> Mary Raub in tech support at Outback told me that the Radian works only in 120/240 single-phase, although they are stackable in parallel.
> 
> Someone in Schneider tech support told me that the XW can be used in three-phase, up to six units (36 kW). Setup instructions are in Appendix D of the XW installation guide, found online at http://www.global-download.schneider-electric.com/85257849002EB8CB/all/5CC689CC3CB7FD10852578BF005EA759/$File/xw-hybrid-inverter-charger_installation-guide%28975-0239-01-01_rev-e%29.pdf.
> 
> Thanks, Allan
>  
> Allan Sindelar
> Allan at positiveenergysolar.com
> NABCEP Certified Photovoltaic Installer
> NABCEP Certified Technical Sales Professional
> New Mexico EE98J Journeyman Electrician
> Positive Energy, Inc.
> 3201 Calle Marie
> Santa Fe, New Mexico 87507
> 505 424-1112
> www.positiveenergysolar.com
> 
> On 10/21/2011 2:01 PM, Gary Willett wrote:
> Allan:
> Also, you might consider using six to nine Schneider/Xantrex XW6048 inverters, or  six to nine Outback Radian GS8048 inverters, in a 3-phase configuration, with a common battery bank.
> Also, Schneider/Xantrex has an 80A 600V charge controller that may be advantageous depending on the distance from the PV arrays to the inverters.
> Regards,
> Gary Willett, PE
> Icarus-Engineering LLC
> Icarus Solar Services LLC
> 
> On 10/21/2011 10:17, Allan Sindelar wrote:
> Wrenches,
> We have been asked for a design for an off-grid system to reduce generator runtime for a mountain resort. Initial projections (consumption measurement results not yet available) suggest 15-20 kW of PV and around 30 kW of inverter capacity. However, the generators and existing wiring are three-phase 120/208.
> 
> My assumption is that our only options are a set of six Sunny Islands, or 9-12 Outback GVFX3648s. Are there any other options or approaches that I'm missing?
> 
> Thank you, Allan
> -- 
> Allan Sindelar
> Allan at positiveenergysolar.com
> NABCEP Certified Photovoltaic Installer
> NABCEP Certified Technical Sales Professional
> New Mexico EE98J Journeyman Electrician
> Positive Energy, Inc.
> 3201 Calle Marie
> Santa Fe, New Mexico 87507
> 505 424-1112
> www.positiveenergysolar.com
>  
> 
> 
> 
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